1. Field of the Invention
The present invention relates to a paper cartridge for a printing apparatus, and more particularly, to a paper cartridge removably mounted in a printing apparatus, to contain paper to print thereon and to supply the paper sheet by sheet.
2. Description of the Related Art
Generally, a printing apparatus such as a photocopier or a laser printer includes a paper cartridge to contain paper to be picked-up and supplied to a body of the printing apparatus. The paper cartridge is removably mounted in a body of the printing apparatus such that a pick-up unit supplies the paper contained in the paper cartridge sheet by sheet. Referring FIG. 1, a conventional paper cartridge has a pick-up roller 11 disposed in a cartridge body 10. A pressure plate 13 is disposed under the pick-up roller 11 and is capable of moving upward and downward. Between the pressure plate 13 and a bottom of the cartridge body 10 is disposed a spring 15. Due to a recovering force of the spring 15, the pick-up roller 11 and the pressure plate 13 come into contact with each other with a predetermined pressure. Accordingly, a predetermined pick-up force is exerted on the paper.
Also, the paper cartridge further includes a lever 17 to allow the pressure plate 13 to be separated from the pick-up roller 11, to stack the paper between the pick-up roller 11 and the pressure plate 13.
When the lever 17 is rotated clockwise (as shown in FIG. 1), a protrusion 17a of the lever 17 comes into contact with the pressure plate 13. The lever 17 moves the pressure plate 13 downward, as shown by the dashed line in FIG. 1, and stops the rotation. In this state, the paper is stacked between the pick-up roller 11 and the pressure plate 13. When the lever 17 rotates back to its original position after the paper is stacked, the pressure plate 13 moves upward by a recovering force of the spring 15. Accordingly, the paper comes into contact with the pick-up roller 11 with a predetermined pressure.
In the conventional paper cartridge as constructed above, the paper is stacked on the pressure plate 13 after the pressure plate 13 is separated from the pick-up roller 11 by the rotation of the lever 17. At this time, a user is required to return the lever 17 to the original position to keep a predetermined degree of pressure between the pick-up roller 11 and the pressure plate 13. If the user inadvertently does not return the lever 17 to the original position, the paper is not smoothly picked-up and thus a smooth printing operation cannot be obtained.
Also, since the lever 17 must be separately provided in the paper cartridge, there are difficulties and limitations in designing the paper cartridge.
Also, since the pressure plate 13 on which the paper is stacked is opened to the outside, the paper is easily contaminated with dust and dirt.